There is no joking about a storm, because it poses a huge danger. Every now and then we hear about dramatic events related to lightning. Most often, this happens in open spaces, where it is difficult to find shelter, but often the discharges hit buildings, destroying them, posing a huge risk to the household. To prevent this, lightning protection systems are installed.
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Lightning protection systems protect not only against direct lightning strikes, but also against atmospheric overvoltages that can cause expensive damage to electrical installations and electronic devices. The topic is very serious, so we will devote an extensive article to it, pointing out the most important issues. First, we will consider which buildings require a lightning protection system, why is the lightning protection system design so important in a given location? Then we will move on to other important concepts: calculating the lightning hazard index for the PN-EN 62305-2 standard, securing a building with an external LPS and internal installation, the LPL protection level and LPS class in the context of legal standards, calculating the place of installation of air terminals, and current regulations and standards for lightning protection systems. We invite you to read!
On which buildings is a lightning protection installation mandatory?
Lightning protection systems , commonly known as lightning rods, are installed on many buildings, especially where there is such an obligation. It depends on many factors, such as the type of building, its height, purpose and location. Therefore, when installing a lightning protection system, we must remember them. Polish law (Regulation of the Minister of Infrastructure of 12 April 2002 on the technical conditions that buildings and their location should meet) states that a lightning protection system is mandatory on buildings that are particularly exposed to lightning strikes, which could consequently cause a threat of tragic consequences - for human health, the environment and property. The installation of a lightning protection system should therefore take into account these guidelines, so the technical conditions that they should meet must be observed.
Taking this into account, we mean industrial and storage facilities, especially those where flammable materials are stored. These are also buildings with large roof surfaces that are exposed to lightning strikes. This also applies to tall residential buildings, over 20 meters, public utility buildings (schools, hospitals, offices, etc.) and historical and historic buildings that, due to their value, require special protection.
How to correctly calculate the lightning hazard index for the PN-EN 62305-2 standard?
For lightning protection to be effective, it must not only be properly installed, but also selected for lightning hazard. To do this, the lightning hazard index for the PN-EN 62305-2 standard must be calculated correctly. The lightning hazard index (LRI) is the most important parameter that allows you to determine whether a given building requires a lightning protection system, and if so, what level should be used. The PN-EN 62305-2 standard describes in detail the methodology for this index. To do this, we must take into account several key factors. One of them is, of course, the type and height of the building. The higher they are, the higher the risk of lightning strike. The same can be said about the surface area. The larger it is, the higher the risk of a dangerous strike.
Another parameter is the location of buildings, because those located in areas with high density of lightning discharges are more susceptible to lightning strikes. For example, we are talking about buildings located high up. The purpose of the building is also an extremely important factor, because those in which many people live or dangerous materials are stored require a higher level of protection. The structural elements and materials used to construct the building are equally important, because they can affect the greater risk during a storm. Objects made of metal are particularly exposed to this risk.
The PN-EN 62305-2 standard contains many detailed tables and formulas. They can be used to calculate the lightning hazard index. By taking into account factors such as location, height and roof area, the probability of a lightning strike hitting a building (N) can be calculated. Another value is the assessment of potential damage (L), where the purpose of the building and the type of materials stored in it are taken into account. On this basis, the hazard index (R) can be calculated using the formula: R = N x L, where R is the level of risk, which allows the degree of lightning protection to be adjusted.
Appropriate building protection with external LPS and internal installation
To effectively protect a building from the effects of a lightning strike, we should use a comprehensive lightning protection system consisting of an external system (LPS - Lightning Protection System) and an internal system. The first of these - the external lightning protection system (LPS) - consists of the following elements:
- Air Terminators - intercept lightning discharges; this may be a pattern of vertical, horizontal or combined coils;
- Down conductors - direct the lightning current from the air terminals to the grounding electrodes. The role of down conductors is therefore extremely important here;
- Lightning earthing rods - conduct lightning current to the ground. We distinguish vertical earthing rods, which are rods driven into the ground, and horizontal earthing rods - copper strips buried in the ground.
The external installation is extremely important, as it is exposed to the front line in the fight against lightning. However, it will not function properly without the internal installation, which includes:
- Surge arresters - protect electrical networks and electronic installations against surges caused by lightning strikes;
- Shielding and grounding - these elements reduce the risk of damage to electrical installations. The issue of grounding is therefore just as important here as the limiters mentioned above. Grounding is therefore the basis in every installation.
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LPL and LPS protection levels and legal standards for lightning protection installations
The lightning protection level (LPL) as well as the lightning protection system class (LPS - Lightning Protection System) define the requirements relating to the lightning protection system in accordance with the PN-EN 62305 standard. As for the LPL, we can define four levels of lightning protection - from LPL I to LPL IV.
The first one - LPL I - means the highest level of protection, recommended for buildings with very high lightning strikes. Following this line, LPL II applies to buildings with high risk, LPL III - with moderate risk, LPL IV - with low risk.
The LPS lightning protection system class specifies detailed technical requirements for the system components. We list class I, which specifies high requirements, the use of the most advanced technologies and materials, as well as lower classes - II, III and IV, which mean lower technical requirements. However, they must always be adapted to the level of protection.
How to calculate the installation location of air terminals?
The location of the air terminals is of great importance for the entire installation, so it must be calculated correctly. To do this, you need to take into account factors such as the type of building, the type of air terminals and the distance between the air terminals.
In the case of the first parameter - type of building - it is about properly placing the air terminals, i.e. in such a way as to cover the entire surface of the building, thus ensuring protection of the structure. In the context of the next aspect - type of air terminal - it is worth knowing that they can be vertical, for example mast, or horizontal, like a lightning rod . The issue is their selection, which depends on the shape of the roof and the specifics of the building. The issue of the distance between the air terminals is equally important. According to the PN-EN 62305 standard, the distances must be selected precisely, so that no point of the roof is outside the protection zone. This de facto means that the air terminals should be placed at appropriate distances. When we are talking about buildings with a low risk level (such as LPL IV), they cannot be greater than 10-15 m. In the case of a higher risk level, these distances must of course be even smaller.
It is worth showing sample calculations, which will bring this subject closer. Let's consider a building measuring 30x40 meters with a flat roof. The LPL III protection level here requires that the distances between air terminals be 10 meters. Therefore, there must be 4 air terminals on the longer side of the roof to cover the entire length. The calculations are therefore as follows: 30m/10m=3. On the shorter side, we must place 5 air terminals, so 40m/10m=4. This gives a total of at least 20 air terminals.
Current regulations and standards for lightning protection installations PN-EN 62305
For a complete picture of this subject, we should also get to know the current regulations and standards of the lightning protection system PN-EN 62305 in detail. This standard consists of four parts: PN-EN 62305-1 (General principles of lightning protection), PN-EN 62305-2 (Risk management and calculation of the lightning hazard index), PN-EN 62305-3 (Physical protection of buildings and installations), PN-EN 62305-4 (Protection of electronic devices in buildings).
With knowledge of these standards, it is also worth knowing about the key requirements for designing and installing the installation, not only in accordance with the PN-EN 62305 standard, but also with the applicable building law regulations. This also applies to materials and components, such as air terminals, down conductors and earthing. All of these elements must meet specific quality requirements and demonstrate impeccable corrosion resistance. It is also important to remember about regular inspections and maintenance to ensure the effectiveness and long-term reliability of the lightning protection installation.
It should also be remembered that the Regulation of the Minister of Infrastructure of 12 April 2002 on the technical conditions that buildings and their location should meet has been slightly amended. This update was aimed at changes in technical standards regarding lightning protection. The provisions amending the regulation concern the use of modern materials and technologies, such as tape and ground wire, which must be made of high conductivity materials. The regulation also contains information on increasing the frequency of inspections and maintenance.
We hope that you have learned the most important things about safety and legal requirements for lightning protection installations. The topic is extremely important, so it is worth knowing it thoroughly.
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